High-gloss multilayer effect pigments having a chromatic interference color and a narrow size distribution, and method for the production thereof

ABSTRACT

Multilayer pearlescent pigments comprising platelet-shaped transparent substrates provided with an optically active coating, where the optically active coating includes at least 
     a) an absorbing high-index layer A having a refractive index n≧1.8
 
b) a low-index layer B having a refractive index n&lt;1.8
 
c) a high-index layer C having a refractive index n≧1.8
 
and also
 
d) optionally at least one outer protective layer D
 
and where the multilayer pearlescent pigments have a cumulative frequency distribution of a volume-averaged size distribution function, with the indices D 10 , D 50 , D 90  and a span ΔD in a range from 0.7-1.4, the span ΔD being calculated in accordance with formula (I)
 
       Δ D =( D   90   −D   10 )/ D   50   (I).
 
     The disclosure further relates to a method for producing these multilayer pearlescent pigments, and also to their use.

The present invention relates to highly lustrous multilayer pearlescentpigments with a chromatic interference color and to a method forproducing the same, and to the use thereof in cosmetic formulations,plastics, films, textiles, ceramic materials, glasses, and coatingcompositions such as paints, printing inks, liquid inks, varnishes orpowder coatings.

The optical effect of effect pigments is based on the directedreflection of light from light-refracting pigment particles which arepredominantly two-dimensional in form and are oriented substantiallyparallel to one another. These pigment particles generally have asubstantially transparent substrate and one or more coatings on thesubstrate. Depending on the composition of the coating or coatings onthe pigment particles, interference, reflection and/or absorptionphenomena produce impressions of color and lightness.

Irregularities in the substrate surface to be coated, or coloredimpurities in or on the substrate, may lead to unwanted scattered-lighteffects and hence to a reduced luster and also to instances of uncleancolor in the end product. Particularly when natural substrate materialsare used, such as natural mica, these unwanted scattered-light effectsand/or colored impurities arise.

The fundamental construction of pearlescent pigments and hence also ofmultilayer pearlescent pigments with an alternating arrangement oflayers of high and low refractive index is known. Reference is made,exemplarily, to patent applications DE 41 41 069 A1, DE 43 19 669 A1, DE196 14 637 A1, DE 198 02 234 A1, DE 198 08 657 A1, DE 198 22 046 A1, DE199 07 313 A1, DE 199 41 253 A1, DE 199 53 655 A1 or DE 102 21 497 A1.

WO 2004/055119 A1 describes interference pigments based on coated,platelet-shaped substrates. The substrates in this case are covered witha first layer of SiO₂, over which is applied, subsequently, a high-indexlayer, consisting for example of TiO₂, ZrO₂, SnO₂, Cr₂O₃, Fe₂O₃ orFe₃O₄, or an interference system comprising alternating high-index andlow-index layers. The pigments may optionally also have an outerprotective layer. In this way, silver-white interference pigments, orinterference pigments with brilliant interference colors, are obtained,which are notable for performance properties, such as mechanicalstability and photo stability, but which do not have a high gloss. Thecolor of the interference pigments is not dependent or is only minimallydependent on the angle.

Thermally and mechanically stable metal oxide-coated effect pigmentsbased on thin glass flakes with a thickness ≦1.0 μm are known from WO2002/090448 A2. The effect pigments may be covered with one or morehigh-index and/or low-index layer(s). The glass flakes possess asoftening temperature of ≧800° C.

Goniochromatic luster pigments are described in EP 0 753 545 B2. Atleast one layer stack comprising a colorless low-index coating and areflecting, selectively or nonselectively absorbing coating, and also,optionally, an outer protective layer, is applied here to a multiplycoated, high-index, nonmetallic, platelet-shaped substrate. The layerthickness of the low-index colorless coating reduces as the number oflayer stacks applied to the substrate increases. The goniochromaticluster pigments exhibit an angle-dependent color change between two ormore intense interference colors.

In accordance with WO 2004/067645 A2, a transparent substrate is coatedwith an uneven number—at least three—of layers of high and lowrefractive index in alternation. The difference in refractive indexbetween the adjacent layers is at least 0.2. At least one of the layersdiffers in its optical thickness from the others. The resultingmultilayer effect pigments therefore do not possess a layer constructionin which the optical thickness of each layer is an uneven multiple of aquarter of the light wavelength for interference (no“quarter-wave-stack” construction).

Multilayer interference pigments with strong interference colors and/orwith a strong angular dependency of the interference colors, consistingof a transparent base material coated with alternating layers of metaloxides of low and high refractive index, are described in EP 0 948 572B1. The difference in the refractive indices is at least 0.1. The numberand thickness of the layers are dependent on the desired effect and onthe substrate used. Considering the construction TiO₂—SiO₂—TiO₂ on amica substrate, for example, pigments with a blue interference color areobtained when optically thin TiO₂ and SiO₂ layers with a layer thickness<100 nm are used, said pigments being more strongly colored than pureTiO₂-mica pigments. The incidence of thick SiO₂ layers with a layerthickness >100 nm produces pigments having a strongly pronounced angulardependency of the interference color.

The optical properties of effect pigments can be influenced, accordingto WO 2006/110359 A2, by a suitable particle size distribution. Theglass flakes described here, classified and coated with a single metaloxide layer, have a D₁₀ of at least 9.5 μm, preferably of 9.5 μm. Adisadvantage is that the pigments have to have a size range with a D₉₀of not more than 85 μm, preferably of about 45 μm.

The prior art discloses various multilayer pearlescent pigments whichpossess appealing optical properties. Nevertheless, there continues tobe a demand for improved products.

It is an object of the present invention to provide multilayerpearlescent pigments with improved luster. The multilayer pearlescentpigments ought additionally to have a relatively high chroma.

Multilayer pearlescent pigments with a color flop ought as far aspossible to have a higher color flop than the multilayer pearlescentpigments from the prior art.

The object has been achieved through provision of multilayer pearlescentpigments, comprising platelet-shaped transparent substrates providedwith an optically active coating, where the optically active coatingcomprises at least

a) an absorbing high-index layer A having a refractive index n≧1.8,b) a low-index layer B having a refractive index n<1.8c) a high-index layer C having a refractive index n≧1.8and alsod) optionally at least one outer protective layer D and where themultilayer pearlescent pigments have a cumulative frequency distributionof a volume-averaged size distribution function, with the indices D₁₀,D₅₀, D₉₀ and a span ΔD from a range of 0.7-1.4, the span ΔD beingcalculated in accordance with formula (I)

ΔD=(D ₉₀ −D ₁₀)/D ₅₀  (I).

Preferred developments are specified in dependent claims 2 to 10.

The object has additionally been achieved through provision of a methodfor producing the multilayer pearlescent pigments of the invention,where the method comprises the following steps:

-   (i) size-classifying the platelet-shaped transparent substrates to    be coated, so that the platelet-shaped transparent substrates to be    coated have a volume-averaged size distribution function with the    characteristics D₁₀, D₅₀, D₉₀, and a span ΔD in a range of 0.7-1.4,    the span ΔD being defined in accordance with the formula    ΔD=(D₉₀−D₁₀)/D₅₀,-   (ii) applying at least the layers A to C to the platelet-shaped    transparent substrates, and also, optionally, at least one layer D,    or-   (iii) applying at least the layers A to C to the platelet-shaped    transparent substrates, and also, optionally, at least one layer D,-   (iv) size-classifying the platelet-shaped transparent substrates to    be coated, so that the platelet-shaped transparent substrates to be    coated have a volume-averaged size distribution function with the    characteristics D₁₀, D₅₀, D₉₀, and a span ΔD in a range of 0.7-1.4,    the span ΔD being defined in accordance with the formula    ΔD=(D₉₀−D₁₀)/D₅₀.

According to one preferred variant of the invention, the platelet-shapedtransparent substrates to be coated are first of all size-classified inaccordance with step (i) and then in step (ii) at least the layers A toC and optionally at least one layer D are applied to the platelet-shapedtransparent substrates.

Further provided by the invention is the use of the multilayerpearlescent pigments of the invention in cosmetic formulations,plastics, films, textiles, ceramic materials, glasses, and coatingcompositions such as paints, printing inks, varnishes, and powdercoatings.

The object on which the invention is based is also achieved throughprovision of an article, where the article comprises or has themultilayer pearlescent pigments of any of claims 1 to 10.

The invention accordingly likewise provides preparations, such ascosmetic formulations, plastics, ceramic materials, glasses, or coatingcompositions such as paints, printing inks, varnishes, and powdercoatings, which comprise the multilayer pearlescent pigments of theinvention. The invention is also directed to articles which areprovided—coated or printed, for example—with the multilayer pearlescentpigments of the invention. Accordingly, coated articles, such asbodyworks, facing elements, etc., or printed articles, such as paper,card, films, textiles, etc., are likewise part of the present invention.

Multilayer pearlescent pigments having improved gloss are understood forthe purposes of this invention to be multilayer pearlescent effectpigments which have at least three coatings on a transparentplatelet-shaped substrate, where these at least three coatings are

a) an absorbing high-index layer A having a refractive index n≧1.8,b) a low-index layer B having a refractive index n<1.8,c) a high-index layer C having a refractive index n≧1.8.

Suitable platelet-shaped transparent substrates to be coated arenonmetallic, natural or synthetic platelet-shaped substrates. Thesubstrates are preferably substantially transparent, more preferablytransparent, which means that they are at least partly transmissive tovisible light.

In accordance with the invention, the layer A is internal in the layerarrangement, i.e., is facing the platelet-shaped transparent substrate;the layer B is situated between the layer A and the layer C, and thelayer C, based on the platelet-shaped transparent substrate, is externalin the layer arrangement.

Between the platelet-shaped transparent substrate and the layer A theremay be one or more further, preferably substantially transparent, layersarranged. According to one preferred development, the layer A is applieddirectly to the transparent platelet-shaped substrate.

Between the layer A and the layer B, and also between the layer B andthe layer C, there may be arranged, independently of one another, one ormore further, preferably substantially transparent, layers. According toone preferred development, the layer B is applied directly to the layerA. According to another preferred development, the layer C is applieddirectly to the layer B.

With especial preference, the layer A is applied directly to theplatelet-shaped transparent substrate, the layer B directly to the layerA, the layer C directly to the layer B, and also, optionally, the layerD directly to the layer C.

The inventors have surprisingly observed that the multilayer pearlescentpigments of the invention, i.e., pearlescent pigments with the specifiedlayer arrangement and a span ΔD according to formula I in the range from0.7 to 1.4, exhibit an extremely strong gloss. According to one furthervariant of the invention, the multilayer pearlescent pigments of theinvention also have a high chroma at an observation angle close to thespecular angle, preferably 15°.

The provision of multilayer pearlescent pigments with a strong lusterand preferably also a high chroma at the same time has hitherto not beenpossible in the art.

The fact that the span ΔD, as defined in claim 1, might have aninfluence on the luster is unexpected in light of the published priorart. The present invention accordingly allows the provision ofmultilayer pearlescent pigments which have extremely appealing opticalproperties.

In the prior art, the span ΔD was not hitherto recognized as anessential feature. Conventional multilayer pearlescent pigmentstherefore have a broad span.

The size distribution of the multilayer pearlescent pigments ischaracterized in accordance with the invention by using the span ΔD,defined as ΔD=(D₉₀−D₁₀)/D₅₀ (formula I). The smaller the span, thenarrower the size distribution.

The D₁₀, D₅₀ or D₉₀ value in the cumulative frequency distribution ofthe volume-averaged size distribution function, as is obtained by laserdiffraction methods, indicates that 10%, 50%, and 90%, respectively, ofthe multilayer pearlescent pigments have a diameter which is the same asor smaller than the respectively indicated value. In this case, the sizedistribution curve is determined using an instrument from Malvern(instrument: Malvern Mastersizer 2000) in accordance with manufacturerindications.

In this instrument, the scattered light signals were evaluated inaccordance with the theory of Mie, which also includes refraction andabsorption behavior on the part of the particles (FIG. 1).

The multilayer pearlescent pigments of the invention possess a span ΔDin a range from 0.7 to 1.4, preferably in a range from 0.7 to 1.3, morepreferably in a range from 0.8 to 1.2, very preferably in a range from0.8 to 1.1. In further-preferred embodiments the span ΔD is in a rangefrom 0.85 to 1.05.

Where the multilayer pearlescent pigments have a span ΔD of more than1.4, the multilayer pearlescent pigments obtained are not highlylustrous. Multilayer pearlescent pigments below a span ΔD of 0.7 arevery complicated to prepare by the usual techniques, and hence can nolonger be produced economically.

The span ΔD of the platelet-shaped transparent substrate to be coatedcorresponds substantially to that of the multilayer pearlescent pigmentof the invention and is ≦1.4, preferably ≦1.3, more preferably ≦1.2,very preferably ≦1.1, and especially preferably ≦1.05.

The multilayer pearlescent pigments of the invention may have anydesired average particle size (D₅₀). The D₅₀ values of the multilayerpearlescent pigments of the invention are situated preferably within arange from 3 to 350 μm. The multilayer pearlescent pigments of theinvention preferably have a D₅₀ value from a range from 3 to 15 μm orfrom a range from 10 to 35 μm or from a range from 25 to 45 μm or from arange from 30 to 65 μm or from a range from 40 to 140 μm or from a rangefrom 135 to 250 μm.

The D₁₀ values of the multilayer pearlescent pigments of the inventionencompass preferably a range from 1 to 120 μm. The multilayerpearlescent pigments of the invention preferably have the combinationsof D₁₀, D₅₀, and D₉₀ values that are indicated in table 1. In thiscombined only in such a way as to produce a span ΔD from a range from0.7 to 1.4, preferably from a range from 0.7 to 1.3, more preferablyfrom a range from 0.8 to 1.2, very preferably from a range from 0.8 to1.1, and especially preferably from a range from 0.85 to 1.05.Combinations of D₁₀, D₅₀, and D₉₀ values that lead to a span ΔD which isnot situated in the range ΔD from 0.7 to 1.4 are not inventiveembodiments.

TABLE 1 Preferred combinations of ranges of the D₁₀, D₅₀, and D₉₀ valuesD₁₀ (μm) D₅₀ (μm) D₉₀ (μm) 1-5  3-15  8-25  5-25 10-35 20-45 10-30 25-4540-70 20-45 30-65  70-110 25-65  40-140 120-180  75-110 135-250 400-490

In this context it has emerged, surprisingly, that the size of themultilayer pearlescent pigments, characterized with the D₅₀ value, isnot critical, and instead that the span ΔD=(D₉₀−D₁₀)/D₅₀ is in a narrowrange from 0.7 to 1.4. The D₅₀ values of the multilayer pearlescentpigments may be, for example, 15, 20, 25 or 30 μm or else 50, 80, 100,150, 200, 250, 300 or 350 μm.

According to one preferred embodiment of the invention, the multilayerpearlescent pigments exhibit only one (number: 1) interference color.With this variant of the invention, therefore, there is substantially noangle-dependent switch between two or more interference colors. When theviewing angle is changed, there is a change in the lightness of theinterference color—for example, from light to dark or vice versa—butthere is no switch in the interference color. The multilayer pearlescentpigments of the invention according to this variant, therefore, do nothave an angle-dependent interference color switch. If a paint or inklayer, in addition to the multilayer pearlescent pigments of theinvention in accordance with this variant, also comprises other colorpigments, the perceived color may undergo angle-dependent change, butthis is not a switch between interference colors, but instead is aswitch between an interference color and the absorption color of thecolor pigments additionally present.

According to another preferred embodiment of the invention, themultilayer pearlescent pigments have at least two interference colors.With this variant of the invention, therefore, there is anangle-dependent switch between two or more interference colors. When theviewing angle is changed, therefore, there is a change in theinterference color—for example, from red to green. The multilayerpearlescent pigments of the invention according to this variant thushave an angle-dependent interference color switch and may also bereferred to as goniochromatic multilayer pearlescent pigments.

According to a further preferred embodiment of the invention, themultilayer pearlescent pigments of the invention do not have a silverinterference color. A feature of the multilayer pearlescent pigments ofthe invention is that they are preferably colored at a near-specularviewing angle, but are not silver-colored. The multilayer pearlescentpigments of the invention therefore differ significantly not only fromsilver-colored interference pigments but also from metallic effectpigments, especially from, for example, silver-colored aluminum effectpigments.

The multilayer pearlescent pigments of the invention preferably have atleast one interference color which is selected from the group consistingof yellow, violet, blue, red, green, and gradations thereof, but whichdoes not include a silver interference color. The interference color inquestion may range from dark to light.

Multilayer pearlescent pigments without a silver interference color areunderstood for the purposes of this invention to be multilayerpearlescent pigments whose chroma values C*₁₅ are >20.

The chroma values here are determined from the following applications: anitrocellulose varnish (Dr. Renger Erco Bronzemischlack 2615e; Morton)containing 6% by weight of multilayer pearlescent pigments, the % byweight figure being based on the total weight of the varnish, isapplied, depending on D₅₀ value, in a wet film thickness in accordancewith table 2, to BYK-Gardner black/white drawdown charts (Byko-Chart2853), and subsequently dried at room temperature. Then, using aBYK-MAC, colorimetric evaluations are performed on these drawdowncharts, with measurement taking place on the black background of thedrawdown chart. The incident angle is 45° and the chroma value employedis that at an observation angle of 15°.

TABLE 2 Wet film thickness as a function of the D₅₀ value of themultilayer pearlescent pigments D₅₀ value Wire doctor <40 μm 36 μm 40μm-85 μm 76 μm >85 μm 100 μm 

The multilayer pearlescent pigments of the invention are notable for astrong luster and also preferably, at the same time, for a high chromaC*₁₅>20.

According to one preferred variant of the invention, the chroma C*₁₅ ofthe multilayer pearlescent pigments of the invention is at least 22,preferably at least 24, more preferably at least 25. A chroma in therange from 24 to 50 has proven very suitable.

Suitable platelet-shaped transparent substrates to be coated arenonmetallic, natural or synthetic platelet-shaped substrates. Thesubstrates are preferably substantially transparent, more preferablytransparent, which means that they are at least partly transmissive tovisible light.

According to one preferred embodiment of the invention, theplatelet-shaped transparent substrates may be selected from the groupconsisting of natural mica, synthetic mica, glass flakes, SiO₂platelets, Al₂O₃ platelets, polymer platelets, platelet-shaped bismuthoxychloride, platelet-shaped substrates comprising a hybridorganic-inorganic layer, and mixtures thereof. The platelet-shapedtransparent substrates are preferably selected from the group consistingof natural mica, synthetic mica, glass flakes, SiO₂ platelets, Al₂O₃platelets, and mixtures thereof. With particular preference theplatelet-shaped transparent substrates are selected from the groupconsisting of natural mica, synthetic mica, glass flakes, and mixturesthereof. Especially preferred are glass flakes and synthetic mica, andmixtures thereof.

In contrast to synthetic platelet-shaped transparent substrates, naturalmica possesses the disadvantage that contaminations, as a result ofincorporated extraneous ions, may alter the hue, and that the surface isnot ideally smooth but instead may have irregularities, such as steps,for example. Even when a natural substrate is used, however, it hassurprisingly emerged that the luster of a plurality of multilayerpearlescent pigments can be increased when the span ΔD is in a rangefrom 0.7 to 1.4, as compared with a plurality of conventional,broad-span multilayer pearlescent pigments.

Synthetic substrates such as, for example, glass flakes or syntheticmica, in contrast, have smooth surfaces, a uniform thickness within anindividual substrate particle, and sharp edges. Consequently the surfaceoffers only a few scattering centers for incident and reflected light,and accordingly, after coating, allows more highly lustrous multilayerpearlescent pigments than with natural mica as substrate. If they arecoated in accordance with the invention with high-index and low-indexlayers, this results in very uniform colors. All of these effectsadvantageously contribute to obtaining highly chromatic multilayerpearlescent pigments having pronounced gloss. Glass flakes used arepreferably those which are produced by the methods described in EP 0 289240 A1, WO 2004/056716 A1, and WO 2005/063637 A1. The glass flakesubstrates which can be used may have, for example, a composition inaccordance with the teaching of EP 1 980 594 B1.

The average geometric thickness of the platelet-shaped transparentsubstrates to be coated is in a range from 50 nm to 5000 nm, preferablyin a range from 60 nm to 3000 nm, and more preferably in a range from 70nm to 2000 nm. In one embodiment, the average geometric thickness forglass flakes as the substrate to be coated is in a range from 750 nm to1500 nm. Glass flakes of this kind are available commercially on a broadbasis. Further advantages are offered by thinner glass flakes. Thethinner substrates result in a lower overall layer thickness of themultilayer pearlescent pigments of the invention. Preference istherefore likewise given to glass flakes whose average geometricthickness is in a range from 100 nm to 700 nm, more preferably in arange from 150 nm to 600 nm, very preferably in a range from 170 nm to500 nm, and especially preferably in a range from 200 nm to 400 nm. Inanother embodiment, the average geometric thickness for natural orsynthetic mica as the substrate to be coated is preferably in a rangefrom 100 nm to 700 nm, more preferably in a range from 150 nm to 600 nm,very preferably in a range from 170 nm to 500 nm, and especiallypreferably in a range from 200 nm to 400 nm.

If platelet-shaped transparent substrates below an average geometricthickness of 50 nm are coated with high-index metal oxides, then themultilayer pearlescent pigments obtained are extremelyfracture-sensitive, and may completely fragment even duringincorporation into the application medium, with the consequence of asignificant reduction in luster. Above an average geometric substratethickness of 5000 nm, the multilayer pearlescent pigments may become toothick overall. This is accompanied by a poorer specific opacity, i.e.,surface area hidden per unit weight of multilayer pearlescent pigment ofthe invention, and also by a lower plane-parallel orientation in theapplication medium. The result of a poorer orientation, in turn, is areduced luster.

The average geometric thickness of the platelet-shaped transparentsubstrate is determined on the basis of a cured varnish film in whichthe multilayer pearlescent pigments are aligned substantiallyplane-parallel to the substrate. For this purpose, a ground section ofthe cured varnish film is investigated under a scanning electronmicroscope (SEM), the geometric thickness of the platelet-shapedtransparent substrate of 100 multilayer pearlescent pigments beingdetermined and averaged statistically.

In the multilayer pigments of the invention, the optical effects arebrought about by the layer structure having the layers A to C, on whichincident light produces the perceptible color effects by physicaleffects such as reflection, interference, absorption, light diffraction,etc.

As optically active layers or coatings it is preferred to apply layerswhich comprise metal oxides, metal oxide hydrates, metal hydroxides,metal suboxides, metals, metal fluorides, metal oxyhalides, metalchalcogenides, metal nitrides, metal oxynitrides, metal sulfides, metalcarbides or mixtures thereof. According to one preferred variant, theoptically active layers or coatings consist of the aforementionedmaterials.

The terms layers or coatings are used interchangeably for the purposesof this invention, unless otherwise indicated.

The refractive index of the high-index layers A and C is in each casen≧1.8, preferably n≧1.9, and more preferably n≧2.0. The refractive indexof the low-index layer B is n<1.8, preferably n<1.7, and more preferablyn<1.6.

In accordance with the invention, the layer A is an absorbing high-indexlayer. This layer A may be selectively absorbing—that is, absorbing in anarrow wavelength range. The layer A may also be nonselectivelyabsorbing, i.e., absorbing over the entire wavelength range of visiblelight.

In the multilayer pearlescent pigments of the invention, the layer C maybe absorbing or nonabsorbing. If the layer C is absorbing, the layer Cmay be selectively absorbing or nonselectively absorbing, as set outabove in relation to the layer A. The layer C may have an identicalchemical composition to the layer A. The layer C, however, may also havea chemical composition which is different from the layer A.

A nonabsorbing layer C may also be referred to as a transparent layer.

Examples of suitable high-index, selectively absorbing materials include

-   -   colored metal oxides or metal oxide hydrates such as iron(III)        oxide (α- and/or γ-Fe₂O₃, red), FeO(OH) (yellow), chromium(III)        oxide (green), titanium(III) oxide (Ti₂O₃, blue), vanadium        pentoxide (orange),    -   colored nitrides such as titanium oxynitrides and titanium        nitride (TiO_(x)N_(y), TiN, blue), the lower titanium oxides and        nitrides generally being present in a mixture with titanium        dioxide,    -   metal sulfides such as cerium sulfide (red),    -   iron titanates such as pseudobrookite (brownish red) and/or        pseudorutile (brownish red),    -   tin-antimony oxide Sn(Sb)O₂,    -   nonabsorbing, colorless, high-index materials, e.g., metal        oxides such as titanium dioxide and zirconium dioxide that are        colored with selectively absorbing colorants. This coloration        may be accomplished by incorporation of colorants into the metal        oxide layer, by the doping thereof with selectively absorbing        metal cations or colored metal oxides such as iron(III) oxide,        or by coating of the metal oxide layer with a film comprising a        colorant.

Examples of high-index, nonselectively absorbing materials include

-   -   metals such as molybdenum, iron, tungsten, chromium, cobalt,        nickel, silver, palladium, platinum, mixtures thereof or alloys        thereof,    -   metal oxides such as magnetite Fe₃O₄, cobalt oxide (CoO and/or        CO₃O₄), vanadium oxide (VO₂ and/or V₂O₃), and also mixtures of        these oxides with metals, more particularly magnetite and        (metallic) iron,    -   iron titanates such as ilmenite,    -   metal sulfides such as molybdenum sulfide, iron sulfide,        tungsten sulfide, chromium sulfide, cobalt sulfide, nickel        sulfide, silver sulfide, tin sulfide, mixtures of these        sulfides, mixtures of these sulfides with the respective metal,        such as MoS₂ and Mo, and mixtures with oxides of the respective        metal, such as MoS₂ and molybdenum oxides,    -   nonabsorbing, colorless, high-index layers such as titanium        dioxide or zirconium dioxide into which nonselectively absorbing        material (e.g., carbon) has been incorporated or which are        coated therewith.

The high-index, nonabsorbing materials include, for example,

-   -   metal oxides such as titanium dioxide, zirconium dioxide, zinc        oxide, tin dioxide, antimony oxide, and mixtures thereof,    -   metal hydroxides,    -   metal oxide hydrates,    -   metal sulfides such as zinc sulfide,    -   metal oxyhalides such as bismuth oxychloride.

The layers A and/or C may in each case also be mixtures of differentselectively and/or nonselectively absorbing components, preferably metaloxides. For example, the different components, preferably metal oxides,may be present in the form of a homogeneous mixture. It is alsopossible, however, for one component to be present in the othercomponent in the form of a dope.

For example, in the layer A and/or C, there may be a nonabsorbingcomponent present, titanium oxide for example, preferably TiO₂, as adope in a selectively absorbing component, preferably Fe₂O₃, and/or in anonselectively absorbing component, Fe₃O₄ for example. Alternatively, aselectively absorbing component, Fe₂O₃ for example, and/or anonselectively absorbing component, Fe₃O₄ for example, may be present asa dope in a nonabsorbing component, titanium oxide for example,preferably TiO₂.

It is of course also possible that mixtures of more than two components,as demonstrated above, are present in the layer A and/or C.

One preferred embodiment uses metal oxides, metal hydroxides and/ormetal oxide hydrates as high-index layer A and/or C. Particularpreference is given to the use of metal oxides. With very particularpreference, the layer A comprises iron oxide and the layer C titaniumdioxide and/or iron oxide and also mixtures thereof. In one embodiment,the layer A is composed of iron oxide and the layer C of titaniumdioxide and/or iron oxide and also mixtures thereof.

Where the multilayer pearlescent pigments of the invention have acoating with titanium dioxide, the titanium dioxide may be present inthe rutile or anatase crystal modification. The titanium dioxide layeris preferably in the rutile form. The rutile form can be obtained by,for example, applying a layer of tin dioxide to the platelet-shapedtransparent substrate to be coated, before the titanium dioxide layer isapplied. Titanium dioxide crystallizes in the rutile modification onthis layer of tin dioxide. This tin dioxide may take the form of aseparate layer, in which case the layer thickness may be a fewnanometers, as for example less than 10 nm, more preferably less than 5nm, even more preferably less than 3 nm.

Nonabsorbing materials are suitable as low-index layer B. Thesematerials include, for example,

-   -   metal oxides such as silicon dioxide, aluminum oxide, boron        oxide,    -   metal oxide hydrates such as silicon oxide hydrate, aluminum        oxide hydrate,    -   metal fluorides such as magnesium fluoride,    -   MgSiO₃.

The low-index metal oxide layer may optionally comprise alkali metaloxides and/or alkaline earth metal oxides as constituents.

The low-index layer B preferably comprises silicon dioxide. In oneembodiment, the low-index layer B consists of silicon dioxide.

The interference-capable coating may either envelop the substratecompletely or may be present only partially on the substrate. Themultilayer pearlescent pigments of the invention are distinguished bythe uniform, homogeneous construction of the coating which envelops theplatelet-shaped substrate completely and covers not only its top andbottom faces.

The individual layers of the multilayer pearlescent pigments of theinvention may each be designed as λ/4 layers. It has surprisinglyemerged, however, that it is not necessary for the layers to have to bedesigned as λ/4 layers in order for highly lustrous and preferably alsohighly chromatic multilayer pearlescent pigments to be obtained. It isthe span of the size distribution that is the key parameter forobtaining highly lustrous and preferably also high-chroma multilayerpearlescent pigments.

The optical thickness of the nonmetallic layers with high and lowrefractive indices determines the optical properties of the multilayerpearlescent pigments. The number and thickness of the layers may be setdepending on the desired effect and the substrate used.

If n is the refractive index of a layer and d is its thickness, theinterference color in which a thin layer appears is given by the productof n and d, i.e., the optical thickness. The colors of such a film thatcome about in the reflecting light under normal light incidence resultfrom a strengthening of the light of the wavelength

$\lambda = {{\frac{4}{{2N} - 1} \cdot n}\; d}$

and by attenuation of light of the wavelength

${\lambda = {{\frac{2}{N} \cdot n}\; d}},$

where N is a positive integer. The variation in color that occurs withincreasing film thickness results from the strengthening or attenuationof particular wavelengths of the light through interference.

In the case of multilayer pigments, the interference color is determinedby the strengthening of particular wavelengths, and, if two or morelayers in a multilayer pigment possess the same optical thickness, thecolor of the reflecting light becomes more intense as the number oflayers increases. In addition, a particularly strong variation of thecolor may be achieved depending on the viewing angle by suitablyselecting the layer thickness of the low-index layer B. A pronouncedcolor flop can thus be developed.

The multilayer pearlescent pigments of the invention may have opticallayer thicknesses of the high-index layers A and C which are in eachcase in the range from 30 nm to 900 nm, preferably in the range from 40nm to 880 nm, and more preferably in the range from 50 nm to 850 nm. Theoptical layer thickness of the low-index layer B may be in a range from30 nm to 500 nm.

In the case of metals, the geometric layer thicknesses of the layer Aand/or C are 10 nm to 50 nm, preferably 15 nm to 30 nm. The layerthicknesses must be set such that the layers have semitransparentproperties. Depending on the metal used, this may result in differentlayer thicknesses.

The layer thicknesses indicated in this application are, unlessotherwise indicated, the optical layer thicknesses. By an optical layerthickness is meant, in accordance with the invention, the product ofgeometric layer thickness and the refractive index of the material whichconstitutes the layer. As the value for the refractive index of thematerial in question, the value known in each case from the literatureis used. In accordance with the invention, the geometric layer thicknessis determined on the basis of SEM micrographs of ground sections ofvarnishes containing multilayer pearlescent pigments orientedplane-parallel to the substrate.

Preferred developments of the invention encompass the following layersequences applied to the platelet-shaped transparent substrate,beginning with the layer A, then layer B, and finally layer C:

1. Layer A: selectively absorbing and high-index

-   -   Layer B: low-index    -   Layer C: selectively absorbing and high-index        2. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index    -   Layer C: selectively absorbing and high-index        3. Layer A: selectively absorbing and high-index    -   Layer B: low-index    -   Layer C: nonselectively absorbing and high-index        4. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index    -   Layer C: nonselectively absorbing and high-index        5. Layer A: selectively absorbing and high-index    -   Layer B: low-index    -   Layer C: nonabsorbing (transparent) and high-index        6. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index    -   Layer C: nonabsorbing (transparent) and high-index

The layer sequences specified above may in each case also have at leastone outer protective layer D, which is optionally organochemicallymodified.

According to one preferred development of the present invention, thelayer B in the layer sequences specified above has an optical layerthickness (or path length) of ≦150 nm, preferably of <140 nm, morepreferably of <130 nm. An optical layer thickness of the layer B in therange from 30 nm to ≦150 nm, preferably in the range from 40 nm to 140nm, and more preferably in the range from 50 nm to 130 nm has provenvery suitable.

If the optical layer thickness of the layer B is ≦150 nm, the multilayerpearlescent pigments of the invention have substantially noangle-dependent interference color. In this embodiment, the multilayerpearlescent pigments of the invention have only one interference color,with its intensity changing from light to dark in dependence on theviewing angle. With this variant of the multilayer pearlescent pigmentsof the invention, therefore, highly lustrous and highly chromatic effectpigments are obtained.

According to a further preferred development of the present invention,in the layer sequences specified above, the layer B has an optical layerthickness of >150 nm, preferably of >180 nm, more preferably of >220 nm.An optical layer thickness of the layer B in the range from >150 nm to500 nm, preferably in the range from 180 nm to 480 nm, and morepreferably in the range from 220 nm to 450 nm has proven very suitable.

If the optical layer thickness of the layer B is >150 nm, the multilayerpearlescent pigments of the invention have an angle-dependentinterference color. In this embodiment, the multilayer pearlescentpigments of the invention have at least two interference colors independence on the viewing angle. With this embodiment of the multilayerpearlescent pigments of the invention, they may also be referred to asgoniochromatic pearlescent pigments. In this variant of the multilayerpearlescent pigments of the invention, therefore, highly lustrouspearlescent pigments with an intense color flop are obtained. Thesemultilayer pearlescent pigments, for example, may have an interferencecolor switch from red to green or from blue to yellow.

The transition between multilayer pearlescent pigments with no colorflop, weak color flop, and intense color flop in dependence on theoptical layer thickness of the low-index layer B is a fluid one. As theoptical layer thickness of the low-index layer B increases, above 150nm, initially, multilayer pearlescent pigments are obtained which haveonly a weak color flop, which ultimately, as the optical layer thicknessof layer B continues to rise, turns into an intense color flop. Anintense color flop typically extends over a plurality of quadrants inthe CIELab color coordinate system.

According to one preferred development of the invention, the followingembodiments are particularly preferred:

1. Layer A: selectively absorbing and high-index

-   -   Layer B: low-index, optical layer thickness ≦150 nm, preferably        from a range from 30 nm to 140 nm    -   Layer C: selectively absorbing and high-index        2. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index, optical layer thickness ≦150 nm, preferably        from a range from 30 nm to 140 nm    -   Layer C: selectively absorbing and high-index        3. Layer A: selectively absorbing and high-index    -   Layer B: low-index, optical layer thickness ≦150 nm, preferably        from a range from 30 nm to 140 nm    -   Layer C: nonselectively absorbing and high-index        4. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index, optical layer thickness ≦150 nm, preferably        from a range from 30 nm to 140 nm    -   Layer C: nonselectively absorbing and high-index        5. Layer A: selectively absorbing and high-index    -   Layer B: low-index, optical layer thickness ≦150 nm, preferably        from a range from 30 nm to 140 nm    -   Layer C: nonabsorbing (transparent) and high-index        6. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index, optical layer thickness ≦150 nm, preferably        from a range from 30 nm to 140 nm    -   Layer C: nonabsorbing (transparent) and high-index

The layer sequences specified above may each also have at least oneouter protective layer D, which is optionally organochemically modified.In the case of the six embodiments specified above, the optical layerthickness of the layer B, according to one further preferred embodiment,is in the range from 40 nm to 140 nm, more preferably from 50 nm to 130nm. The layer B is preferably silicon oxide, more preferably SiO₂. Thelayer A is preferably iron oxide, and the layer C is preferably TiO₂ fortransparent layers and iron oxide for absorbing layers.

According to a further variant of the invention, multilayer pearlescentpigments are preferred which have an angle-dependent change in theinterference color. In dependence on the viewing angle, these multilayerpearlescent pigments have two or more interference colors and maytherefore be referred to as goniochromatic multilayer pearlescentpigments. Preferred embodiments are indicated below:

1. Layer A: selectively absorbing and high-index

-   -   Layer B: low-index, optical layer thickness >150 nm, preferably        from a range from 165 nm to 450 nm    -   Layer C: selectively absorbing and high-index        2. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index, optical layer thickness >150 nm, preferably        from a range from 165 nm to 450 nm    -   Layer C: selectively absorbing and high-index        3. Layer A: selectively absorbing and high-index    -   Layer B: low-index, optical layer thickness >150 nm, preferably        from a range from 165 nm to 450 nm    -   Layer C: nonselectively absorbing and high-index        4. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index, optical layer thickness >150 nm, preferably        from a range from 165 nm to 450 nm    -   Layer C: nonselectively absorbing and high-index        5. Layer A: selectively absorbing and high-index    -   Layer B: low-index, optical layer thickness >150 nm, preferably        from a range from 165 nm to 450 nm    -   Layer C: nonabsorbing (transparent) and high-index        6. Layer A: nonselectively absorbing and high-index    -   Layer B: low-index, optical layer thickness >150 nm, preferably        from a range from 165 nm to 450 nm    -   Layer C: nonabsorbing (transparent) and high-index

The optical layer thickness B of the aforementioned multilayerpearlescent pigments is preferably in the range from >150 nm to 500 nm,more preferably from 180 nm to 480 nm. Above an optical layer thicknessof 500 nm, the multilayer pearlescent pigment becomes too thick overall.Relatively thick pearlescent pigments may not so readily adopt aplane-parallel orientation in the application medium, and, accordingly,also suffer a loss of luster.

The layer B is preferably composed of silicon oxide, preferably SiO₂.The layer A is preferably selectively absorbing or nonselectivelyabsorbing iron oxide, and the layer C is preferably TiO₂ for transparentlayers and iron oxide for absorbing layers.

In accordance with the invention, the following specific layer sequencesare particularly preferred:

I. Multilayer Pearlescent Pigments with Only One (Number: 1)Interference Color, i.e., without Angle-Dependent Switch of InterferenceColorLayer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: titanium oxide, preferably titanium dioxideLayer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: titanium oxide, preferably titanium dioxide, and selectivelyabsorbing iron oxide, preferably Fe₂O₃Layer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: titanium oxide, preferably titanium dioxide, and nonselectivelyabsorbing iron oxide, preferably Fe₃O₄Layer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: nonselectively absorbing iron oxide, preferably Fe₃O₄, andselectively absorbing iron oxide, preferably Fe₂O₃Layer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: titanium oxide, preferably TiO₂Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃, andtitanium oxide, preferably TiO₂Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: nonselectively absorbing iron oxide, preferably Fe₃O₄, andtitanium oxide, preferably TiO₂Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness ≦150nm, preferably from a range from 40 nm to 140 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃, andnonselectively absorbing iron oxide, preferably Fe₃O₄

The high-index layers A and C for the aforementioned preferredmultilayer pearlescent pigments preferably have independently of oneanother an optical layer thickness of 40 to 880 nm and more preferably50 to 850 nm.

II. Multilayer Pearlescent Pigments with at Least Two InterferenceColors, i.e., with Angle-Dependent Switch of Interference ColorLayer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: titanium oxide, preferably titanium dioxideLayer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: titanium oxide, preferably titanium dioxide, and selectivelyabsorbing iron oxide, preferably Fe₂O₃Layer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: titanium oxide, preferably titanium dioxide, and nonselectivelyabsorbing iron oxide, preferably Fe₃O₄Layer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: nonselectively absorbing iron oxide, preferably Fe₃O₄, andselectively absorbing iron oxide, preferably Fe₂O₃Layer A: selectively absorbing iron oxide, preferably Fe₂O₃Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: titanium oxide, preferably TiO₂Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃, andtitanium oxide, preferably TiO₂Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: nonselectively absorbing iron oxide, preferably Fe₃O₄, andtitanium oxide, preferably TiO₂Layer A: nonselectively absorbing iron oxide, preferably Fe₃O₄Layer B: silicon oxide, preferably SiO₂, optical layer thickness >150nm, preferably 180 to 480 nmLayer C: selectively absorbing iron oxide, preferably Fe₂O₃, andnonselectively absorbing iron oxide, preferably Fe₃O₄

The high-index layers A and C for the aforementioned preferredmultilayer pearlescent pigments preferably have independently of oneanother an optical layer thickness of 40 to 880 nm and more preferably50 to 850 nm.

The multilayer pearlescent pigments may additionally be provided with atleast one outer protective layer D, which further increases thestability of the multilayer pearlescent pigment with respect to light,weather and/or chemicals. The outer protective layer D may also be anaftercoat which facilitates the handling of the pigment on incorporationinto different media.

The outer protective layer D of the multilayer pearlescent pigments ofthe invention may comprise or, preferably, consist of one or two metaloxide layers of the elements Si, Al or Ce. In one variant a siliconoxide layer, preferably SiO₂ layer, is applied as outermost metal oxidelayer. Particular preference here is given to a sequence in which firstof all a cerium oxide layer is applied, which is then followed by anSiO₂ layer, as described in WO 2006/021386 A1, the content of which ishereby incorporated by way of reference.

The outer protective layer D may additionally be organic-chemicallymodified on the surface. For example, one or more silanes may be appliedto this outer protective layer. The silanes may be alkylsilanes havingbranched-chain or unbranched alkyl radicals having 1 to 24 C atoms,preferably 6 to 18 C atoms.

The silanes may alternatively be organofunctional silanes which allowchemical attachment to a plastic, a binder of a paint or of an ink, etc.

The organofunctional silanes which are used preferably as surfacemodifiers and which have suitable functional groups are availablecommercially and are produced, for example, by Evonik and sold under thetrade name “Dynasylan”. Further products may be purchased from Momentive(Silquest silanes) or from Wacker, examples being standard silanes andα-silanes from the GENIOSIL product group.

Examples of these products are 3-methacryloyloxypropyl-trimethoxysilane(Dynasylan MEMO, Silquest A-174NT), vinyltri(m)ethoxysilane (DynasylanVTMO or VTEO, Silquest A-151 or A-171), methyltri(m)ethoxysilane(Dynasylan MTMS or MTES), 3-mercaptopropyltrimethoxy-silane (DynasylanMTMO; Silquest A-189), 3-glycidyloxy-propyltrimethoxysilane (DynasylanGLYMO, Silquest A-187), tris[3-(trimethoxysilyl)propyl] isocyanurate(Silquest Y-11597), bis[3-(triethoxysilyl)propyl)] tetrasulfide(Silquest A-1289), bis[3-(triethoxy-silyl)propyl disulfide (SilquestA-1589, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (SilquestA-186), bis(triethoxysilyl)ethane (Silquest Y-9805),gamma-isocyanatopropyltrimethoxysilane (Silquest A-Link 35, GENIOSILGF40), methacryloyloxymethyltri(m)ethoxysilane (GENIOSIL XL 33, XL 36),(methacryloyloxymethyl(m)-ethyldimethoxysilane (GENIOSIL XL 32, XL 34),(isocyanatomethyl)methyldimethoxysilane,(isocyanato-methyl)trimethoxysilane, 3-(triethoxysilyl)propyl-succinicanhydride (GENIOSIL GF 20),(methacryloyloxy-methyl)methyldiethoxysilane,2-acryloyloxyethylmethyl-dimethoxysilane,2-methacryloyloxyethyltrimethoxy-silane,3-acryloyloxypropylmethyldimethoxysilane,2-acryloyloxyethyltrimethoxysilane,2-methacryloyloxy-ethyltriethoxysilane,3-acryloyloxypropyltrimethoxy-silane,3-acryloyloxypropyltripropoxysilane,3-meth-acryloyloxypropyltriethoxysilane,3-methacryloyloxy-propyltriacetoxysilane,3-methacryloyloxypropylmethyl-dimethoxysilane, vinyltrichlorosilane,vinyltrimethoxy-silane (GENIOSIL XL 10), vinyltris(2-methoxyethoxy)silane (GENIOSIL GF 58), and vinyltriacetoxysilane.

As organofunctional silanes it is preferred to use3-methacryloyloxypropyltrimethoxysilane (Dynasylan MEMO, SilquestA-174NT), vinyltri(m)ethoxysilane (Dynasylan VTMO or VTEO, SilquestA-151 or A-171), methyltri(m)ethoxysilane (Dynasylan MTMS or MTES),beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (Silquest A-186),bis(triethoxysilyl)ethane (Silquest Y-9805),gamma-isocyanatopropyltrimethoxysilane (Silquest A-Link 35, GENIOSILGF40), methacryloyloxy-methyltri(m)ethoxysilane (GENIOSIL XL 33, XL 36),(methacryloyloxymethyl) (m)ethyldimethoxysilane (GENIOSIL XL 32, XL 34),3-(triethoxysilyl)propyl-succinic anhydride (GENIOSIL GF 20),vinyltrimethoxy-silane (GENIOSIL XL 10) and/orvinyltris(2-methoxy-ethoxy)silane (GENIOSIL GF 58).

It is, however, also possible to apply other organo-functional silanesto the multilayer pearlescent pigments of the invention.

It is additionally possible to use aqueous prehydro-lyzates that areobtainable, for example, commercially from Degussa. These include, amongothers, aqueous aminosiloxane (Dynasylan Hydrosil 1151), aqueousamino-/alkyl-functional siloxane (Dynasylan Hydrosil 2627 or 2909),aqueous diamino-functional siloxane (Dynasylan Hydrosil 2776), aqueousepoxy-functional siloxane (Dynasylan Hydrosil 2926),amino-/alkyl-functional oligosiloxane (Dynasylan 1146),vinyl-/alkyl-functional oligosiloxane (Dynasylan 6598), oligomericvinylsilane (Dynasylan 6490) or oligomeric short-chain alkyl-functionalsilane (Dynasylan 9896).

In one preferred embodiment, the organofunctional silane mixturecomprises at least one amino-functional silane as well as at least onesilane without a functional binding group. The amino function is afunctional group which is able to enter into one or more chemicalinteractions with the majority of groups that are present in binders.This may involve a covalent bond, such as with isocyanate functions orcarboxylate functions of the binder, for example, or hydrogen bonds suchas with OH functions or COOR functions, or else ionic interactions. Anamino function is therefore very highly suitable for the purpose of thechemical attachment of the multilayer pearlescent pigment to differentkinds of binders.

For this purpose it is preferred to take the following compounds:3-aminopropyltrimethoxysilane (Dynasylan AMMO; Silquest A-1110),3-aminopropyltriethoxysilane (Dynasylan AMEO),[3-(2-aminoethyl)aminopropyl]tri-methoxysilane (Dynasylan DAMO, SilquestA-1120), [3-(2-aminoethyl)aminopropyl]triethoxysilane,triamino-functional trimethoxysilane (Silquest A-1130),bis(gamma-trimethoxysilylpropyl)amine (Silquest A-1170),N-ethyl-gamma-aminoisobutyltrimethoxysilane (Silquest A-Link 15),N-phenyl-gamma-aminopropyltri-methoxysilane (Silquest Y-9669),4-amino-3,3-dimethyl-butyltrimethoxysilane (Silquest A-1637),N-cyclohexyl-aminomethylmethyldiethoxysilane (GENIOSIL XL 924),N-cyclohexylaminomethyltriethoxysilane (GENIOSIL XL 926),N-phenylaminomethyltrimethoxysilane (GENIOSIL XL 973), and mixturesthereof.

In a further-preferred embodiment, the silane without a functionalbinding group is an alkylsilane. The alkyl-silane preferably has theformula (A):

R_((4-z))Si(X)_(z)  (A)

In this formula, z is an integer from 1 to 3, R is a substituted orunsubstituted, unbranched or branched alkyl chain having 10 to 22 Catoms, and X is a halogen group and/or alkoxy group. Preference is givento alkylsilanes having alkyl chains having at least 12 C atoms. R mayalso be joined cyclically to Si, in which case z is typically 2.

At or on the surface of the multilayer pearlescent pigments of theinvention, in addition to the aforementioned silanes and silanemixtures, there may also be further organic-chemical modifiers arranged,such as, for example, substituted or unsubstituted alkyl radicals,polyethers, thioethers, siloxanes, etc., and mixtures thereof. It is,however, also possible for inorganic-chemical modifiers (e.g., Al₂O₃ orZrO₂ or mixtures thereof) to be applied to the pigment surface, thesemodifiers being able, for example, to increase the dispersibility and/orcompatibility in the respective application medium.

Via the surface modification it is possible, for example, to modifyand/or set the hydrophilicity or hydrophobicity of the pigment surface.For example, via the surface modification, it is possible to modifyand/or set the leafing or nonleafing properties of the multilayerpearlescent pigments of the invention. By leafing is meant that, in anapplication medium, such as a paint or a printing ink, for example, themulti-layer pearlescent pigments of the invention take up a position ator close to the interface or surface of the application medium.

The surface modifiers may also have reactive chemical groups, such as,for example, acrylate, methacrylate, vinyl, isocyanate, cyano, epoxy,hydroxyl or amino groups or mixtures thereof. These chemically reactivegroups allow chemical attachment, especially formation of covalentbonds, to the application medium or to components of the applicationmedium, such as binders, for example. By this means it is possible tomake improvements in, for example, the chemical and/or physicalproperties of cured varnishes, paints or printing inks, such asresistance to environmental influences such as humidity, insolation, UVresistance, etc., or with respect to mechanical influences, examplesbeing scratches, etc.

The chemical reaction between the chemically reactive groups and theapplication medium or components of the application medium may beinduced, for example, by irradiation of energy, in the form of UVradiation and/or heat, for example.

For the incorporation of multilayer pearlescent pigments aftercoatedwith silanes and/or provided with an outer protective layer intocosmetic formulations it is necessary to ensure that the correspondingsilane and/or the material of the outer protective layer is allowable inaccordance with cosmetics law.

The multilayer pearlescent pigments of the invention are suitable moreparticularly for use in cosmetics, such as, for example, body powders,face powders, pressed and loose powder, face makeup, powder cream, creammakeup, emulsion makeup, wax makeup, foundation, mousse makeup, rouge,eye makeup such as eyeshadow, mascara, eyeliners, liquid eyeliners,eyebrow pencil, lipcare stick, lipstick, lip gloss, lip liner,hairstyling compositions such as hairspray, hair mousse, hair gel, hairwax, hair mascara, permanent or semipermanent hair colors, temporaryhair colors, skincare compositions such as lotions, gels, and emulsions,and also nail varnish compositions.

In order to obtain specific color effects it is possible, in thecosmetics applications, to use not only the multilayer pearlescentpigments of the invention but also further colorants and/or conventionaleffect pigments or mixtures thereof in variable proportions.Conventional effect pigments used may be, for example, commercialpearlescent pigments based on natural mica coated with high-index metaloxides (such as, for example, the Prestige product group from Eckart),BiOCl platelets, TiO₂ platelets, pearlescent pigments based on syntheticmica coated with high-index metal oxides or based on glass plateletscoated with high-index metal oxides (such as, for example, the MIRAGEproduct group from Eckart), Al₂O₃, SiO₂ or TiO₂ platelets. Moreover, itis also possible for metallic effect pigments to be added, such as theVisionaire product group from Eckart, for example. The colorants may beselected from inorganic or organic pigments.

A method for producing the multilayer pearlescent pigments of theinvention comprises the following steps:

-   i) size-classifying the platelet-shaped transparent substrates to be    coated, so that the platelet-shaped transparent substrates to be    coated have a volume-averaged size distribution function with the    characteristics D₁₀, D₅₀, D₉₀, and a span ΔD in a range of 0.7-1.4,    the span ΔD being defined in accordance with the formula    ΔD=(D₉₀−D₁₀)/D₅₀,-   (ii) applying at least the layers A to C to the platelet-shaped    transparent substrates, and also, optionally, at least one layer D,    or-   (iii) applying at least the layers A to C to the platelet-shaped    transparent substrates, and also, optionally, at least one layer D,-   (iv) size-classifying the platelet-shaped transparent substrates to    be coated, so that the platelet-shaped transparent substrates to be    coated have a volume-averaged size distribution function with the    characteristics D₁₀, D₅₀, D₉₀, and a span ΔD in a range of 0.7-1.4,    the span ΔD being defined in accordance with the formula    ΔD=(D₉₀−D₁₀)/D₅₀.

If the initial substrates are too large, it is possible, optionally, fora comminuting step to be carried out prior to the size-classifying.

The size-classifying may take place before or after the coating of thesubstrates. Advantageously, however, the substrate is first classifiedand then coated. Size-classifying is carried out, and optionallyrepeated, until the multilayer pearlescent pigments have the sizedistribution according to the invention.

A narrow span ΔD for the substrates may be achieved by suitablecomminuting and/or classifying operations on the platelet-shapedtransparent substrates to be coated. The platelet-shaped transparentsubstrates to be coated may be comminuted, for example, by ball mill,jet or agitator ball mill, edge-runner mill or dissolver. The span ΔD ofthe final fraction can be adjusted by appropriate classifying, such as amultiple wet screening, for example. Other classifying methods includecentrifugation in cyclones or sedimentation from a dispersion.

The comminuting and classifying operations may take place in successionand optionally may be combined with one another. Hence a comminutingoperation may be followed by a classifying operation, which is followedby a further comminuting operation on the fine fraction, and so on.

The metal oxide layers are preferably applied wet-chemically, in whichcase the wet-chemical coating methods developed for the production ofpearlescent pigments may be employed. In the case of wet coating, thesubstrate particles are suspended in water and are admixed with one ormore hydrolyzable metal salts or with a waterglass solution at a pHwhich is suitable for hydrolysis and which is selected such that themetal oxides and/or metal oxide hydrates are precipitated directly onthe substrate to be coated, without any instances of secondaryprecipitation. The pH is typically held constant by simultaneous meteredaddition of a base and/or acid. The pigments are subsequently separatedoff, washed, dried at 50-150° C. for 6-18 hours, and optionally calcinedfor 0.5-3 hours, it being possible for the calcining temperature to beoptimized in terms of the particular coating present. Generallyspeaking, the calcining temperatures are between 500 and 1000° C.,preferably between 600 and 900° C. If desired, the pigments, followingapplication of individual coatings, may be separated off, dried, andoptionally calcined, before then being resuspended for the precipitationof the further layers.

The precipitation of the SiO₂ layer onto the platelet-shaped transparentsubstrate to be coated may be accomplished by addition of a potassium orsodium waterglass solution at a suitable pH. The SiO₂ layer mayalternatively be applied via sol-gel methods, starting fromalkoxysilanes, such as tetraethoxysilane, for example.

The invention is elucidated in more detail below through a number ofexamples, without being confined to these examples.

I PREPARATION OF THE PIGMENTS A Classification of the SubstratesInventive Example 1 Classification of Glass Flakes with Narrow SpanΔD=1.0

A suspension of 200 g of glass flakes (GF100M from Glassflake Ltd) in FDwater (FD=fully demineralized, approximately 3% by weight content) wasclassified on a 100 μm sieve, and the sieve undersize was sieved againon a 63 μm sieve. This sieving procedure was repeated twice with sieveresidue obtained on the 63 μm sieve. This gave a glass flake fractionhaving the following particle size distribution (Malvern Mastersizer2000): D₁₀=50 μm, D₅₀=82 μm, D₉₀=132 μm, span ΔD=1.0.

Comparative Example 1 Classification of Glass Flakes with Broad SpanΔD=2.0

A suspension of 200 g of glass flakes (GF 100M from Glassflake Ltd) inFD water (approximately 3% by weight content) was classified on a 150 μmsieve, and the sieve undersize was sieved again on a 34 μm sieve. Thissieving procedure was repeated twice with sieve residue obtained on the34 μm sieve. This gave a glass flake fraction having the followingparticle size distribution (Malvern Mastersizer 2000): D₁₀=25 μm, D₅₀=88μm, D₉₀=200 μm, span ΔD=1.99.

Inventive Example 2 Classification of Synthetic Mica with Narrow SpanΔD=1.2

A suspension of 200 g of artificial mica Sanbao 10-40 (Shantou F.T.Z.Sanbao Pearl Luster Mica Tech Co., Ltd. China) in FD water (about 3% byweight content) was classified on a 34 μm sieve, and the sieve undersizewas again sieved on a 20 μm sieve. This sieving procedure was repeatedtwice with sieve residue obtained on the 20 μm sieve. This gave a micafraction which had the following particle size distribution (MalvernMastersizer 2000): D₁₀=14 μm, D₅₀=26 μm, D₉₀=45 μm, span ΔD=1.2.

Comparative Example 2 Classification of Synthetic Mica with Broad SpanΔD=3.7

1000 g of commercial unclassified synthetic/artificial mica Sanbao (fromShantou F.T.Z. Sanbao Pearl Luster Mica Tech Co., Ltd. China) wasadmixed with 1000 ml of FD water, and subsequently delaminated forapproximately 1 h in a laboratory edge-runner mill from AmericanCyanamid Company.

The cake was subsequently diluted with FD water to a solids content of25% by weight and treated in a Pendraulik TD 200 laboratory dissolverfor 1 h. In the course of this treatment, care is to be taken to ensurethat, by cooling, the temperature of the suspension does not exceed 80°C.

The suspension was subsequently brought with FD water to a solidscontent of 3% by weight and was sieved on a Sweco Separator laboratorysieve to <250 μm. The resulting mica fraction was then filtered offunder suction on a Büchner funnel, and the filtercake obtained was usedas starting material for further coatings.

This gave a mica fraction having the following particle sizedistribution (Malvern Mastersizer 2000): D₁₀=17.7 μm, D₅₀=74.6 μm,D₉₀=292.3 μm, span ΔD=3.7.

B Preparation of Single-Layer Pigments (Starting Material for MultilayerPearlescent Pigments) Comparative Example 3 Preparation of the StartingMaterial for Inventive Examples 3 and 4

200 g of glass flakes from inventive example 1 were suspended in 2000 mlof FD water and heated to 80° C. with turbulent stirring. The pH of thesuspension was adjusted to 1.9 using dilute HCl, and then a first layerof “SnO₂” was precipitated onto the glass flakes. This layer was formedby addition of a solution consisting of 3 g of SnCl₄×5 H₂O (in 10 ml ofconc. HCl+50 ml of FD water), with simultaneous metered addition of a10% strength by weight NaOH solution in order to keep the pH constant,over a period of 1 h. In order to complete the precipitation, thesuspension was stirred for a further 15 min. Thereafter the pH wasraised to 3.0 using dilute HCl, and then a solution of 42 ml of FeCl₃(280 g Fe₂O₃/l) was metered into the suspension. During the addition,the pH was kept constant at 3.0 by counter-control with 10% strength byweight NaOH solution. This was followed by stirring for 15 min more, byfiltration, and by washing of the filtercake with FD water. Thefiltercake was dried initially at 100° C. and calcined at 650° C. for 30min. This gave a lustrous effect pigment with a silver interferencecolor and a slightly orange-red absorption color.

Comparative Example 4 Preparation of the Starting Material forComparative Examples 6 and 7

200 g of glass flakes from comparative example 1 were suspended in 2000ml of FD water and heated to 80° C. with turbulent stirring. The pH ofthe suspension was adjusted to 1.9 using dilute HCl, and then a firstlayer of “SnO₂” was precipitated onto the glass flakes. This layer wasformed by addition of a solution consisting of 3 g of SnCl₄×5 H₂O (in 10ml of conc. HCl+50 ml of FD water), with simultaneous metered additionof a 10% strength by weight NaOH solution in order to keep the pHconstant, over a period of 1 h. In order to complete the precipitation,the suspension was stirred for a further 15 min. Thereafter the pH wasraised to 3.0 using dilute HCl, and then a solution of 42 ml of FeCl₃(280 g Fe₂O₃/l) was metered into the suspension. This was followed bystirring for 15 min more, by filtration, and by washing of thefiltercake with FD water. The filtercake was dried initially at 100° C.and calcined at 650° C. for 30 min. This gave an effect pigment with asilver interference color and light orange-red absorption color.

Comparative Example 5 Synthetic Mica/Fe₂O₃

200 g of synthetic mica from inventive example 2 were suspended in 2000ml of FD water and heated to 80° C. with turbulent stirring. The pH ofthe suspension was adjusted to 3.0 using dilute HCl, and then a solutionof 230 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered into thesuspension. During the addition, the pH was kept constant at 3.0 bycounter-control with 10% strength by weight NaOH solution. This wasfollowed by stirring for 15 min more, by filtration, and by washing ofthe filtercake with FD water. The filtercake was dried initially at 100°C. and calcined at 750° C. for 30 min. This gave a lustrousbronze-colored pearlescent pigment.

C Preparation of the Multilayer Pearlescent Pigments Inventive Example 3Glass Flakes/Fe₂O₃/SiO₂/Fe₂O₃

200 g of glass flakes from comparative example 3 were suspended in 1400ml of isopropanol and heated to 70° C. with turbulent stirring. Thissuspension was admixed with 75 g of tetraethoxysilane, 75 g of FD water,and 5 ml of 10% strength by weight NH₃ solution. The reaction mixturewas stirred for approximately 12 h, after which it was filtered, and thefiltercake was washed with isopropanol and dried in a vacuum dryingcabinet at 100° C.

100 g of the resulting SiO₂-coated glass flakes were suspended in 700 mlof FD water and heated to 80° C. with turbulent stirring. The pH of thesuspension was adjusted to 1.9 using dilute HCl, and then a first layerof “SnO₂” was precipitated onto the coated glass flakes. This layer wasformed by addition of a solution consisting of 1.5 g of SnCl₄×5 H₂O (in5 ml of conc. HCl+25 ml of FD water), with simultaneous metered additionof a 10% strength by weight NaOH solution in order to keep the pHconstant, over a period of 1 h. In order to complete the precipitation,the suspension was stirred for 15 min more. Thereafter the pH was raisedto 3.0 using dilute HCl, and then a solution of 42.5 ml of FeCl₃ (280 gFe₂O₃/l) was metered into the suspension. This was followed by stirringfor 15 min more, by filtration, and by washing of the filtercake with FDwater. The filtercake was initially dried at 100° C. and calcined at650° C. for 30 min. This gave a highly lustrous multilayer pearlescentpigment having an orange interference color and red absorption color.

Inventive Example 4 Glass Flakes/Fe₂O₃/SiO₂/TiO_(2 (Rutile))

200 g of glass flakes from comparative example 3 were suspended in 1400ml of isopropanol and heated to 70° C. with turbulent stirring. Thissuspension was admixed with 75 g of tetraethoxysilane, 75 g of FD water,and 5 ml of 10% strength by weight NH₃ solution. The reaction mixturewas stirred for approximately 12 h, after which it was filtered, and thefiltercake was washed with isopropanol and dried in a vacuum dryingcabinet at 100° C.

100 g of the resulting SiO₂-coated glass flakes were suspended in 700 mlof FD water and heated to 80° C. with turbulent stirring. The pH of thesuspension was adjusted to 1.9 using dilute HCl, and then a first layerof “SnO₂” was precipitated onto the coated glass flakes. This layer wasformed by addition of a solution consisting of 1.5 g of SnCl₄×5 H₂O (in5 ml of conc. HCl+25 ml of FD water), with simultaneous metered additionof a 10% strength by weight NaOH solution in order to keep the pHconstant, over a period of 1 h. In order to complete the precipitation,the suspension was stirred for 15 min more. Thereafter the pH waslowered to 1.6 using dilute HCl, and then a solution of 85 ml of TiCl₄(200 g TiO₂/l FD water) was metered into the suspension. During thisaddition, the pH was kept constant at 1.6 by counter-control with 10%strength by weight NaOH solution. This was followed by stirring for minmore, by filtration, and by washing of the filtercake with FD water. Thefiltercake was initially dried at 100° C. and calcined at 650° C. for 30min. This gave an extremely highly lustrous effect pigment having agreen interference color.

Comparative Example 6 Glass Flakes/Fe₂O₃/SiO₂/Fe₂O₃

200 g of glass flakes from comparative example 4 were suspended in 1400ml of isopropanol and heated to 70° C. with turbulent stirring. Thissuspension was admixed with 75 g of tetraethoxysilane, 75 g of FD water,and 75 ml of 10% strength by weight NH₃ solution. The reaction mixturewas stirred for approximately 12 h, after which it was filtered, and thefiltercake was washed with isopropanol and dried in a vacuum dryingcabinet at 100° C.

100 g of the resulting SiO₂-coated glass flakes were suspended in 700 mlof FD water and heated to 80° C. with turbulent stirring. The pH of thesuspension was adjusted to 1.9 using dilute HCl, and then a first layerof “SnO₂” was precipitated onto the coated glass flakes. This layer wasformed by addition of a solution consisting of 1.5 g of SnCl₄×5 H₂O (in5 ml of conc. HCl+25 ml of FD water), with simultaneous metered additionof a 10% strength by weight NaOH solution in order to keep the pHconstant, over a period of 1 h. In order to complete the precipitation,the suspension was stirred for 15 min more. Thereafter the pH was raisedto 3.0 using dilute HCl, and then a solution of 42.5 ml of FeCl₃ (280 gFe₂O₃/l) was metered into the suspension. This was followed by stirringfor 15 min more, by filtration, and by washing of the filtercake with FDwater. The filtercake was initially dried at 100° C. and calcined at650° C. for 30 min. This gave a multilayer pearlescent pigment having areddish-orange interference color and a red absorption color.

Comparative Example 7 Glass Flakes/Fe₂O₃/SiO₂/TiO_(2 (Rutile))

200 g of glass flakes from comparative example 4 were suspended in 1400ml of isopropanol and heated to 70° C. with turbulent stirring. Thissuspension was admixed with 75 g of tetraethoxysilane, 75 g of FD water,and 5 ml of 10% strength by weight NH₃ solution. The reaction mixturewas stirred for approximately 12 h, after which it was filtered, and thefiltercake was washed with isopropanol and dried in a vacuum dryingcabinet at 100° C.

100 g of the resulting SiO₂-coated glass flakes were suspended in 700 mlof FD water and heated to 80° C. with turbulent stirring. The pH of thesuspension was adjusted to 1.9 using dilute HCl, and then a first layerof “SnO₂” was precipitated onto the coated glass flakes. This layer wasformed by addition of a solution consisting of 1.5 g of SnCl₄×5 H₂O (in5 ml of conc. HCl+25 ml of FD water), with simultaneous metered additionof a 10% strength by weight NaOH solution in order to keep the pHconstant, over a period of 1 h. In order to complete the precipitation,the suspension was stirred for 15 min more. Thereafter the pH waslowered to 1.6 using dilute HCl, and then a solution of 85 ml of TiCl₄(200 g TiO₂/l FD water) was metered into the suspension. During thisaddition, the pH was kept constant at 1.6 by counter-control with 10%strength by weight NaOH solution. This was followed by stirring for minmore, by filtration, and by washing of the filtercake with FD water. Thefiltercake was initially dried at 100° C. and calcined at 650° C. for 30min. This gave a lustrous effect pigment having a bluish-greeninterference color.

Inventive Example 5 Natural Mica/Fe₂O₃/SiO₂/Fe₂O₃

200 g of synthetic mica from inventive example 2 were suspended in 2000ml of FD water and heated to 80° C. with turbulent stirring. The pH ofthe suspension was adjusted to 3.0 using dilute HCl, and then a solutionof 60 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered into thesuspension. During the addition, the pH was kept constant at 3.0 bycounter-control with 10% strength by weight NaOH solution. In order tocomplete the precipitation, the suspension was stirred for a further 15min. Thereafter the pH was raised to 7.5 using 5% strength by weightNaOH solution, and stirring was carried out for 15 min. A waterglasssolution (185 g of waterglass solution, 24% by weight SiO₂, mixed with207 g of FD water) was then introduced slowly into the suspension andthe pH was kept constant at 7.5. This was followed by further stirringfor 20 min, and the pH was lowered to 3.0 again and then a solution of200 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered into thesuspension. During this addition, the pH was kept constant at 3.0 bycounter-control with 10% strength for 15 min more, by filtration, and bywashing of the filtercake with FD water. The filtercake was driedinitially at 100° C. and calcined at 750° C. for 30 min. This gave avery brilliant, intense, bronze-colored multilayer pearlescent pigment.

Inventive Example 6 Synthetic Mica/Fe₂O₃/SiO₂/TiO_(2 (Rutile))

200 g of synthetic mica from inventive example 2 were suspended in 2000ml of FD water and heated to 80° C. with turbulent stirring. The pH ofthe suspension was adjusted to 3.0 using dilute HCl, and then a solutionof 60 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered into thesuspension. During this addition, the pH was kept constant at 3.0 bycounter-control with 10% strength by weight NaOH solution. In order tocomplete the precipitation, the suspension was stirred for a further 15min. Thereafter the pH was raised to 7.5 using 5% strength by weightNaOH solution, followed by stirring for 15 min. A waterglass solution(185 g of waterglass solution, 24% by weight SiO₂, mixed with 207 g ofFD water) was then introduced slowly into the suspension and the pH waskept constant at 7.5. This was followed by stirring for 20 min more, andthe pH was lowered again to 1.9. Then a layer of “SnO₂” was deposited onthe SiO₂ surface. This layer was formed by addition of a solutionconsisting of 5 g of SnCl₄×5 H₂O (in 10 ml of conc. HCl+50 ml of FDwater), with simultaneous metered addition of a 10% strength by weightNaOH solution in order to keep the pH constant, over a period of 1 h. Inorder to complete the precipitation, the suspension was stirred for afurther min. Thereafter the pH was lowered to 1.6 using dilute HCl, andthen a solution of 280 ml of TiCl₄ (200 g TiO₂/l FD water) was meteredinto the suspension. During this addition, the pH was kept constant at1.6 by counter-control with 10% strength by weight NaOH solution. Thiswas followed by a further 15 min of stirring, by filtration, and bywashing of the filtercake with FD water. The filtercake was initiallydried at 100° C. and calcined at 750° C. for 30 min. This gave a verybrilliant, intense, bronze-coloured multilayer pearlescent pigment.

Comparative Example 8 Synthetic Mica/Fe₂O₃/SiO₂/Fe₂O₃

200 g of synthetic mica from comparative example 2 were suspended in2000 ml of FD water and heated to 80° C. with turbulent stirring. The pHof the suspension was adjusted to 3.0 using dilute HCl, and then asolution of 37.5 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered intothe suspension. During the addition, the pH was kept constant at 3.0 bycounter-control with 10% strength by weight NaOH solution. In order tocomplete the precipitation, the suspension was stirred for a further 15min. Thereafter the pH was raised to 7.5 using 5% strength by weightNaOH solution, and stirring was carried out for 15 min. A waterglasssolution (153 g of waterglass solution, 20% by weight SiO₂, mixed with207 g of FD water) was then introduced slowly into the suspension andthe pH was kept constant at 7.5. This was followed by further stirringfor 20 min, and the pH was lowered to 3.0 again, and then a solution of120 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered into thesuspension. During this addition, the pH was kept constant at 3.0 bycounter-control with 10% strength by weight NaOH solution. This wasfollowed by stirring for 15 min more, by filtration, and by washing ofthe filtercake with FD water. The filtercake was dried initially at 100°C. and calcined at 750° C. for 30 min. This gave a weakly lustrous,bronze-colored multilayer pearlescent pigment.

Comparative Example 9 Synthetic Mica/Fe₂O₃/SiO₂/TiO_(2 (Rutile))

200 g of synthetic mica from comparative example 2 were suspended in2000 ml of FD water and heated to 80° C. with turbulent stirring. The pHof the suspension was adjusted to 3.0 using dilute HCl, and then asolution of 37.5 ml of FeCl₃ (280 g Fe₂O₃/l FD water) was metered intothe suspension. During this addition, the pH was kept constant at 3.0 bycounter-control with 10% strength by weight NaOH solution. In order tocomplete the precipitation, the suspension was stirred for a further 15min. Thereafter the pH was raised to 7.5 using 5% strength by weightNaOH solution, followed by stirring for 15 min. A waterglass solution(153 g of waterglass solution, 20% by weight SiO₂, mixed with 207 g ofFD water) was then introduced slowly into the suspension and the pH waskept constant at 7.5. This was followed by stirring for 20 min more, andthe pH was lowered again to 1.9. Then a layer of “SnO₂” was deposited onthe SiO₂ surface. This layer was formed by addition of a solutionconsisting of 5 g of SnCl₄×5 H₂O (in 10 ml of conc. HCl+50 ml of FDwater), with simultaneous metered addition of a 10% strength by weightNaOH solution in order to keep the pH constant, over a period of 1 h. Inorder to complete the precipitation, the suspension was stirred for afurther min. Thereafter the pH was lowered to 1.6 using dilute HCl, andthen a solution of 300 ml of TiCl₄ (200 g TiO₂/l FD water) was meteredinto the suspension. During this addition, the pH was kept constant at1.6 by counter-control with 10% strength by weight NaOH solution. Thiswas followed by a further 15 min of stirring, by filtration, and bywashing of the filtercake with FD water. The filtercake was initiallydried at 100° C. and calcined at 750° C. for 30 min. This gave a weaklylustrous, bronze-colored multilayer pearlescent pigment.

II PHYSICAL CHARACTERIZATION IIa Angle-Dependent Color Measurements

For the measurement of the chroma values, the multilayer pearlescentpigments were incorporated by stirring, with a level of pigmentation of6% by weight (based on the total weight of the wet varnish), into aconventional nitrocellulose varnish (Dr. Renger Erco Bronzemischlack2615e; from Morton). The multilayer pearlescent pigments were introducedfirst and then dispersed into the varnish using a brush.

The completed varnish was applied on a drawdown apparatus (RK Print CoatInstr. Ltd. Citenco K 101), with a wet film thickness, depending on D₅₀value of the multilayer pearlescent pigment, in accordance with table 2,onto Byk-Gardner black/white drawdown charts (Byko-Chart 2853), andsubsequently dried at room temperature.

Using the multi-angle colorimeter Byk Mac (from Byk Gardener), with aconstant incident angle of 45° (in accordance with manufacturerspecifications), the L* and C* values were determined at differentangles of observation relative to the specular angle. Particularlyrelevant were the observation angles relatively close to the specularangle, at 15° and −15°. The relevant chroma value of the multilayerpearlescent pigments of the invention was taken to be the C*₁₅ value,which was measured at an angle removed by 15° from the specular.

Strongly reflecting samples (ideal mirror case) reflected virtually theentire incident light at the so-called specular angle. Here, the colorof the interference color appeared most strongly. The further from thespecular angle in the course of measurement, the less light and henceinterference effect it was possible to measure.

IIb Gloss Measurements

The gloss is a measure of the directed reflection and can becharacterized using a Micro-Tri-Gloss instrument. More stronglyscattering samples therefore exhibit a low gloss.

The nitro varnish applications from IIa were subjected to measurementusing a Micro-Tri-Gloss gloss meter from Byk Gardner at a measurementangle of 20° for high-gloss samples and at 60° for medium-gloss samples,on a black background. Where the gloss values at 60° were above 70 glossunits, the samples are measured at 20° (Byk-Gardner catalogue 2007/2008,p. 14).

IIc Particle Size Determination:

The size distribution curve was determined using an instrument fromMalvern (instrument: Malvern Mastersizer 2000) in accordance withmanufacturer indications. For this purpose, about 0.1 g of the pigmentin question was placed in the form of an aqueous suspension, withoutaddition of dispersing assistants, and with continual stirring with aPasteur pipette, into the sample preparation cell of the measuringinstrument, and subjected to repeated measurement. From the individualmeasurement results, the resultant averages were formed. The scatteredlight signals in this case were evaluated in accordance with the theoryof Mie, which also includes refraction and absorption behavior of theparticles (FIG. 1).

The average size D₅₀ refers in the context of this invention to the D₅₀value of the cumulative undersize curve of the volume-averaged sizedistribution function, as obtained by laser diffraction methods. The D₅₀value indicates that 50% of the pigments have a diameter which is thesame as or smaller than the stated value, for example 20 μm.

Accordingly, the D₉₀ value indicates that 90% of the pigments have adiameter which is the same as or smaller than the value in question.

Additionally, the D₁₀ value indicates that 10% of the pigments have adiameter which is the same as or smaller than the value in question.

The span ΔD, defined as ΔD=(D₉₀−D₁₀)/D₅₀, gives the breadth of thedistribution.

III RESULTS

TABLE 3 Characterization of the effect pigments Effect Gloss, pigmentConstruction 20° C*₁₅ Span Comparative Glass flake/Fe₂O₃ 62.9 4.1 1.1example 3 Comparative Glass flake/Fe₂O₃ 46.7 4.0 2.0 example 4 InventiveGlass flake/ 79.4 31.5 1.1 example 3 Fe₂O₃/SiO₂/Fe₂O₃ Inventive Glassflake/Fe₂O₃/ 82.5 27.7 1.1 example 4 SiO₂/TiO₂ Comparative Glassflake/Fe₂O₃/ 49.4 22.7 2.0 example 6 SiO₂/Fe₂O₃ Comparative Glassflake/Fe₂O₃/ 50.9 20.4 2.0 example 7 SiO₂/TiO₂

From the data in table 3 it can clearly be seen that the inventiveexamples 3 and 4, with the layer construction glassflake/Fe₂O₃/SiO₂/Fe₂O₃ and glass flake/Fe₂O₃/SiO₂/TiO₂, respectively,and a low span, had a strong gloss gain of 16.5 units and 19.6 units,respectively, in comparison with the starting material (comparativeexample 3). For the comparative examples 6 and 7, with a large span,only a slightly increased gloss value was found in comparison with thestarting material, comparative example 4. The chroma of the inventiveexamples 3 and 4 is also shown to be significantly increased compared tothe comparative examples 6 and 7 with a broad span.

TABLE 4 Characterization of the effect pigments Effect Gloss, pigmentConstruction 60° C*₁₅ Span Inventive synth. mica/Fe₂O₃/ 59.2 33.6 1.2example 5 SiO₂/Fe₂O₃ Inventive synth. mica/Fe₂O₃/ 57.2 25.3 1.2 example6 SiO₂/TiO₂ Comparative synth. mica/Fe₂O₃ 26.4 22.3 1.2 example 5Comparative synth. mica/Fe₂O₃/ 29.3 26.5 3.7 example 8 SiO₂/Fe₂O₃Comparative synth. mica/Fe₂O₃/ 23.9 18.8 3.7 example 9 SiO₂/TiO₂

With the mica-based inventive examples 5 and 6 as well, according totable 4, an extreme gloss increase effect, particularly in relation tothe comparative examples 8 and 9 (same layer construction) with broadspan, is observed. Also apparent here, furthermore, is an additionalgloss increase arising from the multilayer technology in comparison ofinventive example 5 and 6 with comparative example 5.

IV. PERFORMANCE EXAMPLES

In the cosmetic application examples below, the inventive multilayerpearlescent pigments produced by one of the above examples were used.

Example 7 Nail Varnish

INCI name Product name wt % Supplier Phase A 100.00 MultilayerMultilayer 2.00 pearlescent pearlescent pigment pigment Phase B Butylacetate International 98.00 www.internationallacquers.lu (and) ethylLacquers acetate (and) Nailpolish & nitrocellulose Care Base 359 (and)isopropyl alcohol

The multilayer pearlescent pigment can be used in a range from0.1%-10.0% by weight. The balance can be made up with InternationalLacquers Nailpolish.

Phase A and phase B were mixed and then dispensed into an appropriatecontainer.

Example 8 Cream Eyeshadow

INCI name Product name wt % Supplier Phase A 100.00 Castor oil Castoroil 28.70 www.riedeldehaen.com Octyl palmitate Liponate EHP 6.00www.lipochemicals.com Cocos Nucifera Lipovol C-76 7.00www.lipochemicals.com (coconut) oil Beeswax Ewacera 12 6.00www.wagnerlanolin.com Isopropyl lanolate Ewalan IP 5.00www.wagnerlanolin.com Persea gratissima Avocado butter 7.00 www.impag.de(avocado) oil and hydrogenated avocado oil Magnesium stearate Magnesium3.00 www.sigmaaldrich.com stearate Bis-hydroxyethoxy- Dow Corning 7.00www.dowcorning.com propyl dimethicone 5562 carbinol fluidDimethicone/vinyl Dow Corning 5.00 www.dowcorning.com dimethicone 9701cosmetic crosspolymer and powder silica Phenoxyethanol Uniphen P-23 0.30www.induchem.com (and) methylparaben (and) ethylparaben (and)butylparaben Phase B Multilayer Multilayer 25.00 pearlescent pigmentpearlescent pigment

The multilayer pearlescent pigment can be used in a range from 5.0%-30%by weight. The balance can be made up with castor oil.

Phase A was mixed and heated to 85° C., the ingredients of phase B werelikewise mixed together, and then were added to phase A with stirring.After being dispensed into an appropriate container, the mixture wascooled to room temperature.

Example 9 Foundation

INCI name Product name wt % Supplier Phase A 100.00 HydrogenatedRitadecene 9.00 www.ritacorp.com polydecene 20 Caprylic/Capric LiponateGC-K 5.00 www.lipochemicals.com triglyceride Prunus Amygdalus Sweetalmond 4.00 www.jandekker.com Dulcis (sweet oil almond) oil CaprylylSilCare 4.00 www.clariant.com trimethicone Silicone 31M50 Caprylylmethicone SilCare 3.00 www.clariant.com silicone 41M15 Steareth-2 VolpoS2 1.60 www.croda.com Steareth-20 Sympatens 2.40 www.kolb.ch AS/200 GPhase B Talc Talc powder 4.50 www.vwr.com Mica (and) iron Prestige 4.00oxides soft beige Mica (and) titanium Prestige 1.00 www.eckart.netdioxide soft silver Multilayer Multilayer 2.00 pearlescent pigmentpearlescent pigment Phase C Glycerin Pricerine 5.00 www.brenntag.com9090 Aqua Water 53.70 Ammonium Aristoflex 0.40 www.simon-und- acryloyl-AVC werner.com dimethyltaurate/VP copolymer Phase D Propylene glycolNipaguard 0.40 www.simon-und- (and) diazolidinyl PDU werner.com urea(and) methylparaben (and) propylparaben

The multilayer pearlescent pigment can be used in a range from 0.1%-8.0%by weight. The balance can be made up with water.

Phase A and phase B were weighed out separately. Phase A was heated to70° C. with stirring, and phase B was added with stirring. Phase C wasmixed thoroughly until the Aristoflex had dissolved, and then waslikewise heated to 70° C. Phase C was added to phase AB and, aftercooling to 40° C., phase D was added.

Example 10 Pressed Eye Shadow

% INCI Name Product name by wt. Supplier Phase A 100.00 Mica Silk Mica17.00 www.vwr.com Boron nitride Softouch 2.50 www.advceramicscos.com CCS102 Zinc stearate Kemilub EZ-V 7.00 www.undesa.com Talc Talc Powder38.50 www.riedeldehaen.com Multilayer Multilayer 25.00 pearlescentpearlescent pigment pigment Phase B Dimethicone Dow Corning 5.00www.dowcorning.com 200 Fluid 5 cst. Cyclomethicone Dow Corning 5.00www.dowcorning.com (and) 9040 dimethicone Elastomer crosspolymer

The multilayer pearlescent pigment can be used in a range of 5.0%-40.0%by weight. The balance can be made up with talc.

Phase A was mixed in a high-speed mixer at 2500 rpm for 30s. Then phaseB was added and the mixture was mixed in the same mixer at 3000 rpm for60 s. Lastly the powder mixture was shaped by pressing in an eye shadowpress at 150 bar for 30 s.

Example 11 Hair Mascara

INCI name Product name wt % Supplier Phase A 100.00 Polyquaternium-Luviquat FC 905 2.70 www.basf.com 16 (Luviquat Excellence) Propylene1,2-propanediol 1.80 www.vwr.com glycol Methylparaben Methyl-4- 0.20www.sigmaaldrich.com hydroxybenzoate Aqua Water 64.45 Phase B CetearylLanette O 5.00 www.cognis.com alcohol Dimethicone Dow Corning 200 1.00www.dowcorning.com fluid/350 cst Ceteareth-25 Cremophor A 25 2.00www.basf.com Propylparaben Propyl-4- 0.10 www.sigmaaldrich.comhydroxybenzoate Phase C Hydroxy- Klucel G 0.50 www.herc.compropylcellulose Magnesium Veegum HV 0.50 www.rtvanderbilt.com aluminiumsilicate Aqua Water 19.00 Phase D Multilayer Multilayer 2.00 pearlescentpearlescent pigment pigment Phenoxyethanol Phenonip 0.20www.clariant.com (and) methylparaben (and) butylparaben (and)ethylparaben (and) propylparaben (and) isobutylparaben Fragrance Blueshadow 0.05 www.bell-europe.com ÖKO

The multilayer pearlescent pigment can be used in a range from 0.5%-5.0%by weight. The balance can be made up with water of phase A.

Phase A and phase B were heated separately to 80° C., and then phase Bwas added slowly to phase A. In a separate vessel, Klucel and Veegumwere added to the water of phase C. Then phase AB was cooled to 40° C.and, in the course of cooling, phases C and D were mixed in withstirring.

Example 12 Hair Gel

INCI name Product name wt % Supplier Phase A 100.00 Multilayerpearlescent Multilayer 0.10 pigment pearlescent pigment AmmoniumAristoflex AVC 1.40 www.clariant.com acryloyldimethyl- taurate/VPcopolymer Citric acid Citric acid 0.10 www.vwr.com Aqua Water 55.10Phase B PVP Luviskol K30 1.50 www.basf.com powder Propylene glycol,Germaben II 0.20 www.ispcorp.com diazolidinyl, urea, methylparaben,propylparaben Triethanolamine Triethanolamine 1.20 www.vwr.com WaterAqua 40.40

The multilayer pearlescent pigment can be used in a range from0.01%-0.5% by weight. The balance can be made up with water.

The pigment was stirred together with the water of phase A, AristoflexAVP and citric acid were added with stirring, and the composition wasmixed for 15 minutes at a speed of 800 rpm. The ingredients of phase Bwere dissolved until a homogeneous solution was produced, and then phaseB was added to phase A, and the composition was mixed.

1. Multilayer pearlescent pigments, comprising platelet-shapedtransparent substrates provided with an optically active coating,wherein the optically active coating comprises at least (a) an absorbinghigh-index layer A having a refractive index n≧1.8 (b) a low-index layerB having a refractive index n<1.8 (c) a high-index layer C having arefractive index n≧1.8 and also (d) optionally at least one outerprotective layer D and in that the multilayer pearlescent pigments havea cumulative frequency distribution of a volume-averaged sizedistribution function, with the indices D₁₀, D₅₀, D₉₀ and a span ΔD in arange from 0.7-1.4, the span ΔD being calculated in accordance withformula (I)ΔD=(D ₉₀ −D ₁₀)/D ₅₀  (I).
 2. The multilayer pearlescent pigments ofclaim 1, wherein the multilayer pearlescent pigments have no silverinterference color.
 3. The multilayer pearlescent pigments of claim 1,wherein the multilayer pearlescent pigments have a span ΔD in a rangefrom 0.7-1.3.
 4. The multilayer pearlescent pigments of claim 1, whereinan optical layer thickness of layer A is in a range from 30 to 900 nm.5. The multilayer pearlescent pigments of claim 1, wherein an opticallayer thickness of layer B is in a range from 30 to ≦500 nm.
 6. Themultilayer pearlescent pigments of any of claim 1, wherein an opticallayer thickness of layer B is in a range from 30 to 150 nm.
 7. Themultilayer pearlescent pigments of any of claim 1, wherein an opticallayer thickness of layer C is in a range from 30 to 900 nm.
 8. Themultilayer pearlescent pigments of any of claim 1, wherein layers A andC comprise a titanium oxide.
 9. The multilayer pearlescent pigments ofclaim 1, wherein layer B comprises a silicon oxide.
 10. The multilayerpearlescent pigments of any of claim 1, wherein the platelet-shapedsubstrates are selected from the group consisting of natural mica,synthetic mica, glass flakes, SiO₂ platelets, Al₂O₃ platelets, andmixtures thereof.
 11. A method for producing the multilayer pearlescentpigments of claim 1, wherein the method comprises the following steps:(i) size-classifying the platelet-shaped transparent substrates to becoated, so that the platelet-shaped transparent substrates to be coatedhave a volume-averaged size distribution function with thecharacteristics D₁₀, D₅₀, D₉₀, and a span ΔD in a range of 0.7-1.4, thespan ΔD being defined in accordance with formula (I), and (ii) applyingat least the layers A to C to the platelet-shaped transparentsubstrates, and also, optionally, at least one layer D, or (iii)applying at least the layers A to C to the platelet-shaped transparentsubstrates, and also, optionally, at least one layer D, and (iv)size-classifying the platelet-shaped transparent substrates to becoated, so that the platelet-shaped transparent substrates to be coatedhave a volume-averaged size distribution function with thecharacteristics D₁₀, D₅₀, D₉₀, and a span ΔD in a range of 0.7-1.4, thespan ΔD being defined in accordance with formula (I).
 12. (canceled) 13.An article wherein the article comprises the multilayer pearlescentpigments of claim
 1. 14. A preparation wherein the preparation comprisesthe multilayer pearlescent pigments of claim
 1. 15. The multilayerpearlescent pigments of claim 8, wherein the titanium oxide is titaniumdioxide.
 16. The multilayer pearlescent pigments of claim 9, wherein thesilicon oxide is silicon dioxide.